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Link Between Secondhand Smoke and Growth in CF Patients

(From the May 2014 Issue of PediatricsOnline)

Infants with cystic fibrosis who are exposed to secondhand smoke may grow more slowly, have poorer lung function and be at greater risk for certain bacterial infections than infants with the disease who live in smoke-free homes, according to a new study. The research, led by pulmonologists at Nationwide Children’s Hospital, is the first to demonstrate a link between secondhand smoke exposure and growth rates during the first year of life for patients with the devastating disease.

Cystic fibrosis (CF), which affects about 1 in 2,500 Americans, is caused by a malfunction in the CFTR gene, which is responsible for transporting chloride and water across cell membranes. In people with the disease, cells that line the passageways of the lungs, pancreas and other organs produce mucus that is unusually thick and sticky. This mucus clogs the airways, leading to bacterial infections in the lungs, and blocks ducts in the pancreas, reducing insulin production and preventing digestive enzymes from reaching the intestines.

Patients with CF often fall well below the average age-specific growth rate, a result of poor nutrient absorption and increased caloric demands from a systemic illness that ultimately affects most of the major organs. Other studies have shown that even healthy children exposed to secondhand smoke often have stunted growth, so researchers wanted to know if the effect would be more profound on children with CF, says study leader Benjamin T. Kopp, MD, a physician in Pulmonary Medicine and a principal investigator in the Center for Microbial Pathogenesis in The Research Institute at Nationwide Children’s.

They reviewed medical records of infants with cystic fibrosis who were seen in the Newborn Cystic Fibrosis Clinic at Nationwide Children’s between 2008 and 2012. Of 75 infants in the study, 44 percent had at least one parent who smoked in the home.

Researchers examined growth, lung function, chest CT scans and the incidence of bacterial infection at age 4 months and 1 year, then compared the data between infants exposed to secondhand smoke and those who weren’t.

The biggest difference was in growth rates. Infants in smoke-free homes grew about 50 percent more during their first year than infants whose parents smoked.

“We had observed that we had a high incidence of secondhand smoke exposure among many of our patients with cystic fibrosis, and we have a subset of kids who had slow growth despite our best efforts, but it was surprising to see weight and measured growth to be so strongly correlated with secondhand smoke exposure,” Dr. Kopp says.

The review also found striking differences in lung function, with children exposed to cigarette smoke displaying asthmatic tendencies with reversible changes when given a bronchodilator such as albuterol. But perhaps most surprising was the presence of the bacterium MRSA. While no CF patients in non-smoking homes tested positive for MRSA during their first year, as many as 30 percent of infants exposed to secondhand smoke tested positive for the pathogen.

Because this was a retrospective chart review, it’s impossible to know how much smoke the infants were exposed to or whether infants were born to women who smoked during pregnancy. Determining those factors would go a long way toward understanding the true impact smoke exposure may have on CF patients, says Dr. Kopp, who also is an assistant professor of pediatrics for The Ohio State University College of Medicine.

Dr. Kopp and his team plan to explore the subject further by adding secondhand smoke exposure effects to an ongoing study of CF patients. By analyzing hair and blood samples from infancy through age 2, researchers can determine the exact level of secondhand smoke exposure and get more information about parents’ smoking habits. The project is a joint effort between Pulmonary Medicine and Infectious Diseases at Nationwide Children’s.

“We have great advances in our medical technology in treatments and disease detection, but it is really important to pay attention to early factors that can impact growth and long-term indicators of disease,” Dr. Kopp says, “and secondhand smoke could be one of them.”